The present invention relates to a dual function exercise machine and, more particularly, to a device for enabling unilateral and bilateral exercise of opposing or corresponding limbs.
Typically, prior art exercising machines provided means for bilateral exercising only. A bilateral exercise is one wherein the opposing limbs apply a force to the same lifting mechanism and move in the same direction at the same rate throughout the entire exercise stroke. Such bilateral exercise machines do not permit maximum development of strength in each limb since when performing exercises bilaterally, only the then dominant limb is functioning at maximum force. For example, if a person trains bilaterally to do a 300 pound bench press, he cannot necessarily lift 150 pounds with each arm.
This problem can be overcome by unilateral training where each arm is trained separately to lift 150 pounds. An athlete who trains each arm separately to lift 150 pounds would have sufficient strength to lift more than 300 pounds using both arms together.
Bilateral training devices are further deficient in that they do not permit training in a natural pattern of movement. In most athletic activities, one limb initates the movement or direction of force, and before it completes the full range of movement, the opposite limb begins the same or similar pattern of movement. For example, in throwing a shotput, broadjumping or pitching a baseball, one limb moves in one direction while the opposing limb moves in the opposite direction. In addition, one limb accelerates while the opposing limb decelerates. Bilateral exercise does not allow training in this natural pattern of movement. However, by training unilaterally, the athlete is able to maximize strength in the limbs and to condition them to perform in the same neuromuscular pattern of movement in which corresponding athletic activities are performed.
If a bilateral device is employed to exercise one limb at a time, besides the inconvenience of changing the weights constantly the user's balance will be shifted to require the user to assume an abnormal position.
Bilateral exercise devices are also inefficient for purposes of rehabilitating an injured limb. Exercising using bilateral devices to rehabilitate an injured limb is usually a very time consuming process since the injured limb cannot contribute much force to the single weight which both the injured and non-injured limb lift. Research has proven that conditioning one limb automatically increases the strength and size in the opposite limb. This effect is known as "cross extensor reflex". In administering therapy to an injured limb, training the noninjured limb provides an automatic neuromusclar transfer of strength to the injured limb. The injured limb therefore proportionately gains in strength and size. This "cross extensor reflex" therefore permits rapid rehabilitation of the injured limb. However, bilateral devices will not permit separate and simultaneous loading of each limb to provide this more rapid rehabilitation. The unilateral machine of this invention, on the other hand, allows the non-injured limb to exercise at maximum capacity while the injured limb is simultaneously exercised at its maximum but lesser capacity.